The proposed career development plan is designed to equip the PI with unique skill sets, expand knowledge base and research experience to meet the short-term goal of becoming a productive researcher and a long- term goal of becoming an independent investigator in monocyte/macrophage biology in the areas of obesity, diabetes mellitus and cardiovascular disease (CVD). The plan will be carried out at the University of Kentucky (UK), an institution that is renowned for its strong CVD research program. The PI will be mentored by Dr. Susan Smyth, the Chief of Cardiovascular Medicine and co-mentored by Dr. Phil Kern, the Director of Barnstable Brown Diabetes and Obesity Center. The plan proposes to explore the relationship between monocytosis, adipose tissue (AT) inflammation and its impact on atherosclerosis using insights the PI recently gained from studies at Columbia University. The PI has found that neutrophil-derived damage associated molecular patterns (DAMP), such as S100A8/A9 drives myelopoiesis and severely affects atherosclerotic lesion regression in diabetes. Further, he found a dramatic increase in the mRNA expression of both S100A8 and S100A9 in white AT from obese mouse models. However, unlike in type I diabetic mouse models, the circulating levels of S100A8 and S100A9 in obese models are neither increased nor driven by hyperglycemia. Why S100A8 and S100A9 are increased in AT and whether they are involved in obesity-induced monocytosis is not clear. The overall goal of this project is to understand how obesity affects the number and phenotype of circulating WBCs, particularly the monocytes and, in turn, arterial biology. We will use mouse models to study the mechanisms driving these human abnormalities, develop a proof of concept for a treatment strategy aimed at reducing the offending DAMPs or cytokines, and assess whether this strategy will alter atherosclerosis in mouse models. Finally, we will determine whether insights developed in mice correlate with changes in humans. Specific Aim 1 will determine the sources of cells and signaling molecules in AT that drives monocyte production in obesity. In this aim, we will also determine the effect of adiposity and impact of weight loss on myelopoiesis and characterize the phenotype of circulating monocytes in mouse models of obesity. Specific Aim 2 will identify the processes and signaling pathways that mediate obesity-induced monocytosis. Specific Aim 3 will assess the impact of obesity-induced monocytosis on atherosclerotic lesion regression. Collectively the outcomes of this project will provide novel insights into the causes and consequences of enhanced monocytosis in obesity.